皮肤癌-Skin Cancer

Other risk factors
Other factors which increase the risk of developing melanoma include the following.

• A family history. If a close blood relative develops melanoma then your risk is increased. This may be because you may inherit fair skin which is more easily sun damaged. However, other genetic factors are thought to play a part in some cases. Two 'faulty genes' which may be inherited have been found which are known to increase the risk or melanoma. Further research aims to clarify the role of these and other genes which may be involved. As a rule, if you have a family history of melanoma you should take extra care to protect your skin from sun damage. Also, check your skin regularly for early signs of melanoma.
• Common moles. These are the small brown marks which occur on almost everybody. They are caused by a collection of melanocytes in the skin surface. If you have many (60 or more) you have an increased risk that one will develop into a melanoma.
• Atypical (non-typical) moles. Some people have larger moles which are often irregular in shape and are usually brown or black. You have an increased risk of developing melanoma if you have one of these. In particular, if you have a strong family history of melanoma (father, mother, brother or sister with a melanoma), and you have an atypical mole, you have a very high risk of developing melanoma. Make sure you check your skin regularly.
• Using sunbeds or similar tanning machines which emit UV light.

What are the symptoms of melanoma?

A typical melanoma starts as a small dark patch on the skin. It can develop from a normal part of skin, or from an existing mole. A melanoma is often different to a mole in one or more of the following ways (summed up as ABCD) - that is:

• Asymmetry - the shape of a melanoma is often uneven and asymmetrical, unlike a mole which is usually round and even.
• Border - the border or edges of a melanoma are often ragged, notched or blurred. A mole has a smooth well-defined edge.
• Colour - the colour (pigmentation) of a melanoma is often not uniform. So there may be 2-3 shades of brown or black. A mole usually has one uniform colour.
• Diameter - the size of a melanoma is usually larger than a normal mole, and it continues to grow.

However, some melanomas are not dark, and some melanomas are not typical in how they look. As a melanoma grows in the skin it may itch, bleed, crust or ulcerate.

The 'take home message' is: see a doctor if you develop a lump or patch on the skin which you are unsure about, or if an existing mole changes in its shape, border, colour, or size.

A melanoma can develop on any area of skin. Rarely, they develop in the iris or back of the eye. (Unlike non-melanoma skin cancers, melanomas often develop on areas of skin not often exposed to the sun. These areas may have had short spells of sun damage such as during a holiday.)

If some cells break off and spread (metastasize) to other parts of the body, various other symptoms can develop. A common early symptom of spread is for the nearby lymph glands (nodes) to swell.

How is a melanoma diagnosed?

If a melanoma is suspected then your doctor is likely to advise an 'excisional biopsy'. This is where the entire abnormal area of skin is removed by a minor operation. (Local anaesthetic is injected into the skin to make this painless.) This tissue is looked at under the microscope. This is to:

• Confirm the diagnosis - abnormal melanoma cells can be seen.
• To assess the thickness of the melanoma (how deep it has spread into the skin.) The thickness of the melanoma helps to guide treatment and the need for further assessment.

Initial treatment and assessment of melanoma

The excisional biopsy may be curative
When doing an excisional biopsy (described above) the doctor will remove a margin of normal skin around the melanoma. When the biopsy is looked at under the microscope, if the doctor is sure that all the melanoma cells have been removed, and the melanoma cells are confined to the top layer of skin, then no further treatment may be needed. Otherwise, a second operation called a 'wide local excision' is usually advised.

Wide local excision may be needed
This aims to remove an area of normal skin around where the melanoma had been (before it was removed with excisional biopsy). This aims to make sure that any cells which may have grown in the local area of skin have been removed. The amount of normal looking skin removed varies - depending on the thickness of the melanoma (how deep it has spread into the skin) as reported from the biopsy. It may be 1-2 cm around where the melanoma had been.

This operation may be done under local or general anaesthetic. In some cases a skin graft may be needed to cover the wound.

Staging of melanoma
The aim of staging is to find out how much a cancer has grown and spread. Finding out the stage of the cancer helps doctors to advise on the best treatment options. It also gives a reasonable indication of outlook (prognosis). (See separate leaflet called 'Cancer Staging and Grading' for details)

The common staging system used for melanoma divides it into four stages:

• Stage one is when the melanoma is just in the top layer of skin, it is less than 1.5 mm thick, and there is no spread to anywhere else in the body.
• Stage two is when the melanoma is just in the top layer of skin but is over 1.5 mm thick, or there are some cancer cells in nearby parts of the skin less than 5 cm away from the main (primary) tumour. There is no spread to other parts of the body.
• Stage three is when some cancer cells have spread to the nearby lymph glands (nodes), or some cancer cells have spread to areas of nearby skin more than 5 cm away from the main tumour.
• Stage four is when some cancer cells have spread to other parts of the body such as the lung, liver, bone, etc.

Most cases of melanoma are diagnosed at stage one when there is a very good chance that treatment will cure the condition.

How is melanoma assessed and staged
If the initial biopsy and the tissue taken from the wide local excision show that the melanoma is just in the top layer of skin and is less than 0.76 mm thick, then no further tests are usually needed. It is highly unlikely that it will have spread. This is an early stage one melanoma.

A doctor will examine you to see if you have any swollen lymph nodes (glands) near to the melanoma. If you have, then the melanoma is likely to have spread to these local lymph nodes.

It is possible that there may be some early spread without causing symptoms if the melanoma is thicker than 0.76 mm on the initial biopsy. In particular, there may be spread of some cells to the nearest lymph node without it yet causing it to swell. Therefore, a test called sentinal node biopsy, and sometimes other tests, may be advised.

Sentinal node biopsy. This is a relatively new test. The sentinel lymph node is the nearest node to the melanoma - the one likely to be first affected if cancer cells spread. A sentinel node biopsy is where this node is found, removed, and looked at under the microscope to look for cancer cells. If no cancer cells are detected, the cancer is unlikely to have spread. This test may be done at the same time as treatment with wide excision. It is done by injecting a tiny amount of radioactive liquid and coloured dye into the site of the melanoma. This travels with the lymph to the nearest (sentinel) lymph node. The node can then be detected by using x-rays and a scan for radioactivity. Once the nearest node is found, it is removed by a small operation.

Other tests. Tests which may be advised depend on: if you have symptoms; if the lymph nodes are found to be involved; the thickness of the primary melanoma (the thicker the primary tumour, the greater the chance of spread). The tests aim to detect if the cancer has spread to other parts of the body. For example, you may be advised to have x-rays, blood tests, scans, etc.

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